The present invention relates to an improvement of a carburetor throttle valve control system comprising a throttle lever for opening and closing a throttle valve of a carburetor; and a governor system coupled to the throttle lever. The governor system includes a governor spring that exerts a spring force on the throttle lever in a direction to open the throttle valve, the spring force being adjusted via an output control member by an operator; and a governor that, when an engine is running, exerts an output on the throttle lever in a direction to close the throttle valve, and increases the output in response to an increase in the rotational speed of the engine.